An evidence of Humanin-like peptide and Humanin mediated cryosurvival of spermatozoa in buffalo bulls.

Buffalo spermatozoa are vulnerable to cryo-injuries due to inherent deficiency of endogenous antioxidants, high polyunsaturated fatty acids (PUFA) content in plasma membrane and low cholesterol/phospholipid (C/P) ratio. Humanin is a potent cytoprotective agent that protects the cells against oxidative stress and apoptosis. The present study was designed to establish the presence of Humanin in buffalo and effect of Humanin supplementation on freezability of buffalo spermatozoa. Indirect immunofluorescence test revealed presence of Humanin in ejaculated and epididymal spermatozoa, and, elongated spermatids and interstitial space in the testicular tissue section. Humanin levels in seminal plasma were significantly and positively correlated with sperm concentration and individual progressive motility (IPM) in good (n = 22; IPM >70%) and poor (n = 10; IPM <50%) quality ejaculates. For supplementation studies, a total of 24 ejaculates (IPM ≥70%) were collected and each ejaculate was then divided into four aliquots. First aliquot was diluted with egg yolk-tris-glycerol (EYTG) extender without Humanin and served as control group (Group I). Rest three aliquots were diluted with extender containing 2 (Group II), 5 (Group III) and 10 µM Humanin (Group IV), respectively. Semen was cryopreserved using standard protocol and evaluated at pre-freeze for lipid peroxidation (LPO) and post-thaw stages for spermatozoa kinematics, LPO, mitochondrial membrane potential (MMP), capacitation, apoptotic status and DNA integrity. The treatment group that showed best results (5 µM) was compared with control group for in vitro fertility assessment by homologous zona binding assay. The LPO levels were lower (p < 0.05) in 5 and 10 µM Humanin supplemented group. The MMP and DNA integrity were higher (p < 0.05) in 5 µM group than other groups. F-pattern was higher (p < 0.05) and B-pattern was lower (p < 0.05) in 5 and 10 µM Humanin supplemented groups. Lower apoptotic and higher viable spermatozoa (p < 0.05) were observed in 5 µM Humanin group. The mean number of spermatozoa bound to zona pellucida was higher (p < 0.05) in 5 µM Humanin treated group than the control group. The study established the presence of Humanin in buffalo spermatozoa and seminal plasma for very first time and concluded that Humanin supplementation at 5 µM concentration improves the freezability and in vitro fertility of buffalo spermatozoa.

Supplementation of Mito TEMPO and acetovanillone in semen extender improves freezability of buffalo spermatozoa.

BACKGROUND: Oxidative stress is one of the leading factors responsible for poor post-thaw semen quality because of overproduction of reactive oxygen species (ROS) over neutralizing antioxidants present in semen. Mainly two ROS generation sites are present in spermatozoa, that is, mitochondria and plasma membrane. Therefore, the idea of targeting these specific sites for minimization of ROS production with the compounds having known mechanism of actions was built up as a core for this research. OBJECTIVE: Present study was done to investigate the effects of Mito TEMPO and acetovanillone individually and in combination on freezability of buffalo spermatozoa. MATERIALS AND METHODS: For the experiment, semen extender was supplemented with Mito TEMPO (50 µM), acetovanillone (50 µM), and a combination of Mito TEMPO + acetovanillone (50 µM+ 50 µM), designated as Group II, Group III, and Group IV, respectively. Control group without any supplementation was designated as Group I. A total of 24 ejaculates with individual progressive motility (IPM) of ≥70% were selected for the study. After final dilution, filling-sealing of straws, equilibration, and freezing were done as per the standard procedure. Semen samples were evaluated for IPM, plasma membrane integrity, lipid peroxidation, total antioxidant capacity (TAC), and cholesterol to phospholipids (C/P) ratio at both fresh and post-thaw stages. Evaluation of ROS, mitochondrial membrane potential (MMP), capacitation status (CTC assay), and in vitro fertility potential were conducted only on frozen-thawed samples. RESULTS: The addition of Mito TEMPO (50 µM) and acetovanillone (50 µM) individually and in combination significantly (p < 0.05) improved post-thaw semen quality in terms of IPM, plasma membrane integrity, TAC, cholesterol content, C/P ratio, MMP, Chlortetracycline (CTC)-Full (F) pattern, and zona binding ability of buffalo spermatozoa, while significantly (p < 0.05) reduced ROS production, lipid peroxidation, and capacitation like changes as compared to the control group. DISCUSSION: As Mito TEMPO acts as an SOD mimetic and also detoxifies ferrous iron at the mitochondria level, it aids in neutralization of excessive ROS production and minimizes oxidative stress-related damages that enhances the antioxidant potential of sperm mitochondria. Earlier studies also indicated improved post-thaw semen quality in 50 µM supplemented group. The improvement observed in acetovanillone (50 µM) group might be because of inhibition of Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase as this enzyme activation by various physical/chemical inducers during cryopreservation process leads to activation of CatSper channel resulting in calcium influx, premature capacitation, and acrosomal reaction like changes through activation of adenylate cyclase and cAMP/PKA-mediated tyrosine phosphorylation of sperm proteins. Acetovanillone also prevents NADPH oxidase-mediated inhibition of glutathione reductase activity, which has a vital role in protecting the structural and functional integrity of sperm plasma membrane. CONCLUSION: Results indicated beneficial effects of supplementation of Mito TEMPO and acetovanillone on sperm freezability and individual supplementation was as efficient as the combination group for sustaining post-thaw semen quality.